Most sputter targets used in the past are so-called planar targets which are formed circularly or rectangularly. These planar targets, however, have the disadvantage that only approximately 30% to 40% of the material of which it is comprised are effectively sputtered.
To increase the effectiveness of sputtering, tubular targets are increasingly employed. Their production, however, is more difficult than the production of planar targets.
A method for the production of a sputtering target is already known, in which, first, a cylindrical carrier element is introduced into a casting mold such that an empty volume is formed between the carrier element and the casting mold (EP 0 500 031 B1).
A target material is hereupon filled into this empty volume between the carrier element and the casting mold and the casting mold is closed. An isostatic hot pressing is subsequently applied onto the target material and the carrier element. Through the isostatic pressing the bonding force between the target material and the outer surface of the carrier element is improved.
A tube cathode for use in a sputter process is furthermore known, which comprises a target carrier and a target, wherein between target carrier and target an electrically and thermally well conducting layer is located (EP 1 752 556 A1). The thermally well conducting layer is herein divided into several individual layers along the longitudinal axis of the target carrier, which layers are spaced apart from one another.
Segmenting a tube target perpendicularly to the longitudinal axis is disclosed in WO 2007/0414125 A2. The cylindrical target herein has a length of more than approximately 36 inches (=approximately 91 cm) and has one or several cylindrical sputter sections. Within the cylindrical target is provided a carrier pipe. A fastening layer of indium is located between the cylindrical sputter target and the cylindrical carrier pipe in order to connect the target with the carrier pipe.
There is furthermore known a tube target with a cylindrical carrier tube and at least one target tube disposed on its shell surface (WO 2006/063721 A1). Herein between the target tube and the carrier tube a connection layer is disposed which is conductive and which has a degree of wetting >90%.
Similar tube targets are disclosed in the following publications: US 2001/0047936 A1; JP 4350161; JP 2006-083408.
The known tube cathodes are heated so strongly during the sputter process that they must be cooled by means of cooling water. Since the requirements made of the power density of tube cathodes becomes increasingly higher, the cooling must also become ever more efficient. Herein large temperature differences occur between the inner wall and the outer wall of the target tube. That is to say the inner wall rests on the outer wall of a carrier tube in whose interior the cooling water is transported, while the outer wall is exposed to the hot plasma. Through the action of the plasma, high temperatures result whereby the target expands. Since the target is simultaneously cooled through the interior cooling, a temperature gradient forms over the thickness of the target. Since, however, the target also expands due to the high temperatures of the plasma, radial tear-off forces occur, which lead to damage or even destruction of the target making uniform coating no longer possible.